[Dune-devel] Building dune-common with gcc-4.8 fails

[Christian Engwer]

Hi Carsten,

Am 7. Juli 2015 07:24:03 MESZ, schrieb "Carsten Gräser" <graeser at mi.fu-berlin.de>:
>Hi Christian,
>
>Am 03.07.2015 um 16:39 schrieb Christian Engwer:
>> Hi Carsten,
>> 
>> I can confirm this behaviour for debian testing.
>that's a little sad, because it means that none of our
>debian-using dev's has lately tested the release branch
>with any but the newest compilers.

that is not actually true.

>> The problem seems to be inherent to mpich, as the mpicc.mpich always
>> uses these flags, regardless of the chosen compiler, this
>> 
>> mpicc -cc=/usr/bin/gcc-4.8 ...
>> 
>> will results in the same problem.
>> 
>> I think we have to work around this. How about just removing all
>> "-f..." options from MPI flags?

the problem does not occurre with openmpi, which many people are using (isn't it even the default?).

>I don't know if this is viable. Maybe some of them are necessary
>to compile with mpi?

Not in this case.

>Unfortunately cmake does not allow to overwrite these flags
>properly. For the moment I use the attached patch and pass
>the corresponding flag via CMAKE_FLAGS.

Not a good option. In particular as we encourage people to use the packages.

I think it is a Debian bug, because also when I change the compiler via the mpicc switch it includes these wrong options.

Christian

>
>Carsten
>
>
>
>> 
>> Christian
>> 
>> On Wed, Jul 01, 2015 at 10:20:57PM +0200, Carsten Gräser wrote:
>>> Am 01.07.2015 um 15:50 schrieb Carsten Gräser:
>>>> Am 01.07.2015 um 15:40 schrieb Jö Fahlke:
>>>>> Am Wed,  1. Jul 2015, 15:35:12 +0200 schrieb Carsten Gräser:
>>>>>> Date: Wed, 01 Jul 2015 15:35:12 +0200
>>>>>> From: Carsten Gräser <graeser at mi.fu-berlin.de>
>>>>>> To: "dune-devel at dune-project.org" <dune-devel at dune-project.org>
>>>>>> Subject: Re: [Dune-devel] Building dune-common with gcc-4.8 fails
>>>>>>
>>>>>> Hi Jö,
>>>>>
>>>>>> CMakeCache shows that this flag is also present in
>MPI_CXX_COMPILE_FLAGS
>>>>>> and MPI_C_COMPILE_FLAGS.
>>>>>
>>>>> In your other Mail you bisected the problem to the patch that
>enabled mpi by
>>>>> default in cmake.  So this sounds very mpi-related.  Maybe that
>flag is
>>>>> extracted from mpicc?  And you don't have a problem before the
>patch because
>>>>> dune-common did not look for mpi then, but is doing it now?
>>>>>
>>>>> Which MPI are you using?
>>>> It's mpich-3.1.
>>>>
>>>> I also noticed that passing the compiler to mpic++ via -cxx
>preserves
>>>> this -fstack-protector-strong option which seems to be the ubuntu
>default.
>>>
>>> I guess I've found the origin of the problem, but I don't now
>>> who's to blame and how to fix this: Recent Ubuntu decided to enable
>>>
>>>   -D_FORTIFY_SOURCE=2  -fstack-protector-strong
>>>
>>> by default for security reasons. This also seems to imply that these
>>> flags are by default used with the mpi compiler wrappers, at least
>>> according to
>>>
>>>   mpicxx -show
>>>
>>> Not surprisingly the cmake module FindMPI detects these flags and
>>> stores them in MPI_C_COMPILER_FLAGS which we forwarded to
>>> MPI_DUNE_COMPILE_FLAGS and thus use when building dune
>>> applications with mpi. The problem is that the second flag is
>>> not supported with gcc versions < 4.9, but the flag is always
>passed.
>>> It's a little unclear, who is to blame for this problem:
>>>
>>> a)Dune is blindly passing the mpi compile flags regardless of the
>>>   selected compiler.
>>>
>>> b)FindMPI does not allow to pass a compiler in order to detect
>>>   suitable flags.
>>>
>>> c)Even "mpicc -cc=/usr/bin/gcc-4.8" does not provide suitable flags.
>>>
>>> d)Is it a ubuntu bug to always provide these flags with mpi,
>>>   regardless of the compiler?
>>>
>>> I'd like to at least circumvent the problem to be able to test
>>> with all my compilers, but it seems that one cannot overwrite
>>> the MPI_C_COMPILER_FLAGS with a command line argument.
>>> For now I have to manually remove the flag in the cache
>>> if I want to test with a packaged but older compiler. Does
>>> anybody more familiar with mpi and cmake now a better way
>>> to get around this?
>>>
>>> Best,
>>> Carsten
>>>
>>>
>> 
>> 
>> 
>>> _______________________________________________
>>> Dune-devel mailing list
>>> Dune-devel at dune-project.org
>>> http://lists.dune-project.org/mailman/listinfo/dune-devel
>> 
>> 
>
>
>-- 
>Prof. Dr. Carsten Gräser
>Freie Universität Berlin
>Institut für Mathematik
>Arnimallee 6
>14195 Berlin, Germany
>phone: +49 30 838 72637
>fax  : +49 30 838 472637
>email: graeser at mi.fu-berlin.de
>URL  : http://page.mi.fu-berlin.de/graeser
>
>
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